Process for the recovery of ammonia from fermentation mashes



Oct. 25, 1932. L. E. CARLSMITH ET AL 1,834,561

PROCESS FOR THE RECOVERY OF AMMONIA FROM FERMENTATION MASHES Filed Sept. 25. 1930 Pump 4a mam/a E Producf' Pump P mp

J //VVE/V7'0/|S. M MC QM BYM KMA ATTORNEY Patented Get. 25, 1932 I Uni-tree STATES PATENT OFFICE LEONARD E. CARLSMITH, BENJAMIN C. BOECKELER, AND IGNACE J. KRGHIMA, OF TERRE HAUTE, INDIANA, ASSIGNORS TO COMMERCIAL SOLVENTS CORPORATION OF TERRE I-IAUTE, INDIANA, A CORPORATION OF MARYLAND PROCESS FOR THE RECOVERY OF AMMONIA FROM FEEMENTATION MASHES Application filed September 25, 1930. Serial No. 484,370.

The present invention relates to the recovery of useful products from dilute aqueous solutions thereof. More particularly, it relates to the recovery, by distillation, of ammonia and salts of organic acids from mashes resulting from the fermentation of cellulosic materials.

In various fermentation processes where acids are produced it is generally necessary to add to the mash from time to time suiticient alkaline material to neutralize the acids being formed in order that the fermentation may proceed to completion. This is particularly the case in the production of propionic and acetic acids by the fermentation of carbohydrates, etc. by means of propionic acidforming bacteria; in the production of buty ric acid by fermenting various carbohydrates and in the so-called Langwell fermentation rocess'. In the latter process, cellulosic material is fermented at temperatures ranging from 50 to 70 U. by means of thermophilic bacteria of the type usually found in stable manure, pond mud, the intestinal tract of herbivorous animals, etc. In order to complete the fermentation it. found necessary to maintain the hydrogen ion concentration of the fermenting mash within the limits QH S and pl-l=9Q A number of different materials may be suitably employed for this purpose, as for example, (a) oxides, hydroxides, carbonates or bicarbonates of alkali metals including the same ammonium com pounds and ammonia, and (b) oxides, hydroxides, carbonates or bicarbonates of alkaline earth metals including magnesium in which cases compounds of alkali metals which cause the formation of insoluble alkaline earth metal compounds are added from time to time. The use of such materials as lime, calcium carbonate or soda ash as the neutralizing medium is naturally much more economical than most of the other compounds enumerated. Calcium compounds, unfortunately, however, have a tendency to slow up the fermentation and soluble alkalies such as soda ash generallyextract so much soluble organic matter from the fermenting cellulosic materials to cause serious difliculties in the recovery of the products of the fermentation. The use of ammonia as the neutralizing agent overcomes most of these disadvantages, but due to its cost can only be employed on a commercial scale for this purpose when some suitable means of recovering the ammonia in a form fit for reuse in the process is available. Such aprocess is hereinafter set forth. It is to be distinctly understood also that the process is similarly applicable to the recovery of ammonia from other dilute solutions of ammonium salts.

' The operation of the present invention may be illustrated by the use of ammonia neutralized .inash from the Langwell fermentation process. The fermentation operation may be carried out substantially. as set forth in U. S. Patents Nos. 1,443,881; 1,602,306; and 1,639,- 571, with the exception that ammonia or an ammonium compound such as the hydroxide, carbonate or bicarbonate, is used as the neutralizing agent with the result that when the fermentation is completed an aqueous mash remains which contains about 2.0 grams per 100 c. c. of ammonium salts of principally acetic, propionic, and butyric acids, and considerable unfermented cellulosic and lignous material, a considerable proportion of which is in such a form as to be separable from the liquid only with difliculty. ,Comminuted cel lulosic material such as corn-cobs, straw, etc. may be used as the raw material, in which case it is generally necessary to add suitable nutrient substances such as distillery wastes like butyl-acetonic fermentation slop or inorganic materials. like potassium sulfate, sodium phosphate, potassium chloride, etc.

In certain other fermentation processes carbohydrates such as starch or sugars are the most suitable raw materials. In such cases it will be necessary to vary somewhat the kind and quantity of nutrient, the operating temperature, hydrogen ion concentration range, etc, depending upon the particular organism used as the means of promoting the fermentation. The present invention, however, is not particularly concerned with these factors and pertains only to the steps relating to neutralizing the fermenting medium with ammonia (including also ammonium hydroxide, carbonate and bicarbonate) and recovering in usable form ammoniaand the other products formed during the fermentations.

In order to recover the ammonia and the organic acid salts from the fermentation mash described above, as much of the cellulosic material as possible is preferably first removed by settling or filtration. To the liquor thus obtained is then added a sufficient amount of a non-volatile base which will react with theammonium salts and give ammonium hydroxide or other easily decomposable ammonium compounds. Materials suitable for this purpose are non-volatile bases such as, for example, lime or calcium carbonate. In case lime is used the mash will at point contain ammonium hydroxide, calcium acetate, calcium propionate, calcium butyrate, etc. together with small amounts of dissolved and suspended organic matter. This material is then fed into a multiple effect evaporator of the type hereinafter described, where the ammonia is recovered and the salt solution concentrated.

Instead of sendin the dilute liquor directly into one of the e ects of the multiple evaporator, as has previously been suggested it has now been discovered that much more efiicient results will be obtained if the dilute liquor is first passed through a scrubbing tower where an appreciable proportion of the ammonia will be removed by the vapors from the first effect of the evaporator. In this way it is possible to remove practically all of the ammonia in the first effect of the evaporator instead of in the first and second clfects, as has previously been suggested. The accompanymg diagram will illustrate the type of apparatus and the method of operation, which it ,is referred to employ although obviously hot 7 may be modified in certain respects without departing from the spirit of the invention.

In the description which follows and in the accompanying diagram the effects of the evaporator have been numbered in the sequence of the vapor flow. However, it should be understood that the liquor may be fed through the s stem in any order, provided the liquor passed through the scrubbing tower always enters the same effect from which the vapor passing through the scrubbing tower is taken.

In operating according to the present procedure the mash containing about 2 grams of say a mixture of calcium acetate, calcium propionate, and calcium butyrate and about 0.6 gram of ammonia per 100 grams of solution is introduced through the opening (a) into the scrubbing column (A) which may be packed with Raschig rings, coke or other suitable packing material, or it may contain bubble caps or perforated plates. As the dilute mash trickles down through the packing material it comes in contact with vapor from the first effect of the multiple evaporator (I) which enters the scrubbing tower at (b) After the system has been in operation for a short time this hot vapor contains some ammonia collected in the first effect. The va or leaving the top of the scrubbing tower at c) and which contains the greater portion of the ammonia, enters the second eifect evaporator (II) at (d) where it serves as the heating medium. The condensate from the heating elements of the various effects is withdrawn at (e), (e) and (e"). The condensate taken from the second effect heating element at (6) will contain the greater portion of the ammonia, as a rule above 96% being recovered at this point, and may be sent to the ammonia still for final treatment or reused directly as a neutralizing agent in succeeding fermentations. A small amount of an'nnonia will also be present in the condensate at (e') and may be sent to the ammonia still or otherwise recovered, but in general the amount present at this point will be too small to justify the cost of its recovery by distillation. In case ammonia is to be recovered from the condensate at ((2'), however, it is necessary, in order to realize the advantages of using the stripping column, that the ammonia from this condensate be distilled separately from that obtained at (e).

The dilute mash from the bottom of the scrubbing tower (A) is pumped by means of the pump (B) into the bottom of the first effect evaporator (I) in which it is heated by means of steam introduced at (f). The condensate from this steam is withdrawn at (g) and returned to the boilers. The dilute mash is circulated through the first effect evaporator as indicated by the arrow, a portion being constantly withdrawn at the by-pass (h) and sent by the pump (C) through the filter (D) where insoluble material such as excess lime or calcium carbonate, unfermented cellulosic material, etc. is removed. The liquor passing through this filter and into the bottom of the secon effect evaporator (II) has been almost completel freed from ammonia. The vapor from the rst effect evaporator (I) and which contains the residual ammonia not removed in the scrubbing tower leaves the separator at (i) and is used as the heating medium for the scrubbin tower. A portion of this vapor may, if esired, be by-passed to the heating unit of the second eifect.

After the removal of the ammonia, the residual liquor passes through additional effects similar to the first effect and in such numbers as may be required to give the desired concentration of the liquor and the most desirable degree of steam economy. In the accompanying diagram four eifects are shown, but it is understood that a lesser or greater number may be employed without any appreciable modification of the operating procedure, except that the liquor is filtered only after it leaves the effect into which the weakest liquor is fed. Under certain circum stances, however, it is sometimes desirable to filter the liquor after the second or third effect, rather than after the first efiect, as for example, when prolonged boiling makes the liquor more easily filtered or when it is more economical to filter a smaller volume of liquid.

The concentrated liquor is by-passed from the last elfect at (y') and removed from the system by meansol the pump (E).

The vapors from the last effect of the evaporator may be condensed by means of the condenser (F) and by the vapor pump (G) or by any other suitable means. i

In case the liquor being treated contains litle or no insoluble impurities it may be bypassed around the filter or the filter may even be omitted from the system. Certain other obvious modifications will naturally occur to one skilled in the art.

It should be understood also that it is not absolutely essential that the process be operated continuously, but may, if desired, be operated as a batch process. For example, the liquor leaving the scrubber may be concentrated to the degree necessary to recover the ammonia or the ammonia and salts in a single evaporator or in the first efiect or two eifects of a multiple efi ect evaporator. Such a process, however, is not as economical from the point of view of steam consumption as the preferred method of using a multiple effect evaporator.

The apparatus employed in the process hereinabove disclosed is claimed in a copending application, U. S. Serial N 0. 484,371, filed September 25, 1930.

lVhat is claimed is: r

1. In the production of ammonia and other useful products from a dilute aqueous solution of ammonium salts, the steps which c0m prise adding to said solution a non-volatile base in sufiicient quantity to liberate the ammonia and form the corresponding salts of the non-volatile base, passing the resulting solution througha scrubber in contact with the vapors resulting from the partial concentration of said solution after leaving said scrubber, condensing the vapors leaving said scrubber whereby the ammonia is obtained in aqueous solution, and further concentrating the partially concentrated solution whereby the salts of the non-volatile base are obtained in concentrated solution.

2. In a process for the recovery of ammonia and salts of aliphatic acids from ammonia-neutralized fermentation liquor, the steps which comprise adding to said liquor a non-volatile base in sufficient quantity to liberate the ammonia and form the aliphatic acid salts or the non-volatile base, passing said liquor through a scrubber in contact with the vapors resulting from the partial of the non-volatile base, passing the resulting solution through a scrubber in contact with the vapors from the first effect of a multiple effect evaporator, partially concentrating the solution leaving the scrubber in the said first effect of the multiple effect evapo- 1 rator, and further concentrating the partially concentrated solution in one or more succeeding effects of the multiple elfect evaporator whereby the ammonia is obtained in aqueous solution as the condensate from the second and succeeding effects and the salts of the non-volatile base are obtained in concentrated solution in the last eifect.

4:. In a process for the recovery of ammonia and salts of aliphatic acids from ammonia-neutralized fermentation liquor, the steps which comprise adding to said liquor a non-volatile base in sufiicient quantity to liberate the ammonia and form the aliphatic acid salts of the non-volatile base, passing said liquor through a scrubber in contact with the vapors from the first effect of a multiple effect evaporator, partially concentrating the liquor leaving the scrubber in the said first effect of the multiple effect evaporator, and further concentrating the liquor in one or more succeeding effects of the multiple effect evaporator whereby the ammonia is obtained in aqueous solution as the condensate from the second and succeeding effects and the aliphatic acid salts of the non-volatile base are obtained in concentrated solution in the last effect.

5. In the production of ammonia and, other useful products from a. dilute aqueous solution of ammonium salts, the steps which compriseadding to said solution a non-volatile base in suflicient quantity to liberate the ammonia and form the corresponding salts of the non-volatile base, passing the resulting solution through a scrubber in contact with the vapors from the first effect of a multiple eifect evaporator, partially concentrating the solution leaving the scrubber in.

the said first effect of the multiple efiect evaporator, filtering the partially concentrated solution to remove insoluble impurities, and further concentrating the partially concentrated solution in one or more succeeding effects of the multiple effect evaporator whereby the ammonia is obtained in aqueous solution as the condensate'from the second and succeeding effects and the salts of the non-volatile base are obtained in concentrated solution in the last effect,

6. In a process for the recovery of ammonia and salts of aliphatic acids from ammonia-neutralized fermentation liquor, the steps which comprise adding to said liquor a non-volatile base in sufficient quantity to liberate the ammonia and form the aliphatic acid salts of the, non-volatile base, passing said liquor through a scrubber in contact with the vapors from the first effect of a multiple effect evaporator, partially concentrating the liquor leaving the scrubber in the said first effect of the multiple effect evaporator, filtering the partially concentrated liquor to remove insoluble impurities, and further concentrating the partially concentrated liquor in one or more succeeding effects of the multiple effect evaporator whereby the ammonia is obtained in aqueous solution as the condensate from the second and succeeding efiects and the aliphatic acid salts of the non-volatile base are obtained in concentrated solution in the last effect.

7. In the production of ammonia and other useful products from a dilute aqueous solution of ammonium salts, the steps which comprise adding to said solution a nonvolatile base in sufficient quantity to liberate the ammonia and form the corresponding salts of the non-volatile base, passing the resulting solution through a scrubber in contact with the vapors from the first effect of a multiple effect evaporator, partially concentrating the solution leaving the scrubber in the said first effect of the multiple effect evaporator, and further concentrating the partially concentrated solution in one or more succeeding effects of the multiple effect evaporator whereby the ammonia is obtained in aqueous solution as the condensate from the second effect and the salts of the non-volatile base are obtfained in concentrated solution in the last ofect.

8. In a process for the recovery of ammonia and salts of aliphatic acids from ammonianeutralized fermentation liquor, the steps which comprise adding to said liquor a nonvolatile base in sufficient quantity to liberate the ammonia and form the aliphatic acid salts of the non-volatile base, passing said liquor through a scrubber in contact with the vapors from the first effect of a multiple effect evaporator, partially concentrating the liquor leaving the scrubber in the said first effect of the multiple effect evaporator, and further concentrating the liquor in one or more succeeding effects of the multiple effect evaporator whereby the ammonia is obtained in aqueous solut1on as the condensate from the second effect and the aliphatic acid salts of the non-volatile base are obtained in concentrated solution in the last effect.

9. In the production of ammonia and other useful products from a dilute aqueous solution of ammonia salts, the steps which comprise adding to said solution a non-volatile base'in sufficient quantity to liberate the ammonia and form the corresponding salts of the non-volatile base, passing the resulting solution through a scrubber in contact with the vapors from the first effect of a multiple effect evaporator, partially concentrating the solution leaving the scrubber in the said first effect of the multiple effect evaporator, filtering the partially concentrated solution to remove insoluble impurities, and further concentrating the partilly concentrated solution in one or more succeeding effects of the multiple effect evaporator whereby the ammonia is obtained in aqueous solution as the condensate from the second effect and the salts of the non-volatile base are obtained in concentrated solution in the last effect.

10. In a process for the recovery of ammonia and salts of aliphatic acids from ammonia-neutralized fermentation liquor, the steps which comprise adding to said liquor a non-volatile base in sufficient quantity to liberate the ammonia and form the aliphatic acid salts of the non-volatile base, passing said liquor through a scrubber in contact with the vapors from the first effect of a multiple effect evaporator, partially concentrating the liquor leaving the scrubber in the said first effect of the multiple effect evaporator, filtering the partially concentrated liquor to remove insoluble impurities, and further concentrating the partially concentrated liquor in one or more succeeding effects of the multiple effect evaporator whereby the ammonia is obtained in aqueous solution as the condensate from the second effect and the aliphatic acid salts of the non-volatile base are oibftained in concentrated solution in the last e ect.

In testimony whereof we affix our signatures.

LEONARD E. CARLSMITH. BENJAMIN C. BOECKELER. IGNACE J. KRCHMA. 

